A technique, which classifies data by a machine learning based on training data, is proposed (for example, patent document 1). The machine learning based on the training data is used for the classifications of the data such as image or document widely. When the plurality of data is classified in one of the plurality of items, a learning device generates a rule (model) indicating feature quantity and its weighting for classification based on the training data. And a classifier calculates score based on the weighting of the feature quantity included in the data as input by the plurality of data and classifies the data in the plurality of items based on the score.